Fuse construction



Sept. 5, 1944. s. l. LINDELL FUSE CONSTRUCTION Original Filed Aug. 2, 1940 Ill Y Il,

i l' 'M porting a terminal retainer 59.

Patented Sept. 5, 1944 FUSE CONSTRUCTION Sigurd I. Lindell, Chicago, Ill., assignor to Schweitzer & Conrad, Inc., Chicago, Ill., a corporation of Delaware Original application August 2, 1940, Serial No. 349,899. Divided and this application August 3, 1942. Serial No. 453,325

7 Claims. (Cl. 200-117) This invention relates, generally, to circuit interrupting apparatus, and it has particular relation to this type of apparatus in which the circuit is opened on the blowing of a fusible section of a conductor. This application is a division of my application Serial No. 349,899, filed August 2, 1940, now Patent No. 2,323,229, issued June 29, 1943.

An object of this invention is to provide for lengthening the arc in a fuse device in a new and improved manner. 1

Another object of this invention is to provide for elongating the arc in a fuse device by moving a roller in a new and improved manner.

It is also an object of this invention to provide for elongating the arc by moving a roller and also to provide an indication that the fuse has operated in a new and improved manner.

4Other objects of this invention will, in part, be obvious and in part appear hereinafter.

For a more complete understanding of the nature and scopeof this invention reference may be had to the following detailed description taken in connection with the accompanying drawing, in which:

Figure l is a longitudinal sectional view of an embodiment of the invention;

Figure 2 is a detail sectional view of the upper end construction of the fuse shown in Figure 1, the view being taken at right angles to that of Figure 1;

Figure 3 is a View similar to that shown in Figure 2 and illustrating the relationship of the parts after the fusible section has blown; and

Figure 4 is a detail sectional view taken along the line 4-4 of Figure 2.

As shown in Figure 1, a tubular housing, illustrated generally at 53, is provided having an inner lining 54 of iiber and an outer lining 55 of Bakelite. Ferrules 58 and 51 are provided at the ends of the housing 53. The ierrule 56 has associated therewith a metallic ring 58 for sup- The terminal retainer 59 carries a terminal 60 which projects through a suitable aperture in the ferrule 56 and is soldered thereto as indicated at 6|. A cloth washer 62 is provided for preventing the escape of marble dust 63 through vent openings 64 in the ierrule 56.

" The marble dust 63 is provided to embed a coil 65 of tungsten wire whose resistance increases whenit is heated to a vpredetermined temperature.

by a generally S-shaped terminal support member 61. The terminal 66 is threaded into an adapter 1| of insulating material, such as fiber, which interiits with a sleeve 13 of insulation such as Bakelite or glass that in turn interts with a cup-shaped metallic retaining member 14 in the upper end of the housing 53.

The terminal 66 is connected to the upper fer rule 51 by a conductor 15 which, for a one ampere fuse, may be formed of Chromel A wire having a. diameter of 0.0113 inch. The conductor 15 extends through a suitable groove in the adapter 1| and is coiled as indicated at 1G about a lava spacer 11 to concentrate heat on a specified portion of the conductor 15. The conductor 15 is looped about a pin 18 that is carried by the adapter 1i and extends through the spacer 11 and through the sleeve 13, and then extends from pin 18 through the spacer 11 and out of the sleeve 13 through an aperture 91 in the retaining member 14. After the conductor 15 leaves the sleeve 13, it is wound about a roller 19 and fastened to an integrally formed tab thereof as shown more clearly in Figures 2 and 4 of the drawing. The spacer 11 and the coil 16 of conductor 15 thereon provide means whereby heat is concentrated on the portion of conductor 15 within spacer 11, assuring that the latter portion of conductor 15 will always fuse or blow rst. The conductor 15 thus comprises'one portion, that within spacer 1,1, which always operates rst to open the circuit between the associated terminals, and another portion, that extending from spacer 11 exterior thereto, which operates following operation of said one or rst portion, as will appear more fully presently.

The roller 19 is mounted for rotation with respect Vto a pin or shaft 8l that is carried by a roller support member 82 and is prevented from rotating with respect thereto by a pin 83. Within the roller 19 there is provided a coil spring 84, one endv 85 of which, as shown in Figure 4, interts with a correspondingly shaped groove in the shaft 8i, and the other end is hooked over a tab 86 that is integrally formed with the roller 19,

The roller support member 82 can be stationarily mounted within the cup-shaped retainer 14. In such case, when the section of the conductor 15 within the lava spacer 11 fuses, the roller 19 would merely revolve under the influence of the coil spring 84 and withdraw the portion of the conductor 15 attached thereto from the sleeve 13 and would wind it upon itself as shown in Figure 3 of the drawing.

In some instances it is desirable to provide an purpose the roller support member 92 is movably mounted within the cup-shaped member 14 and is arranged to be moved outwardly thereof by means of a coil compression spring 99. The roller support member 92 is provided with a cap 9| which is secured thereto by screws 92.. The cap 9| projects out of the ferrule 51, as shown in Figure 3 of the drawing, when the fuse has operated to indicate that the fuse-should be replaced. A cloth washer 93 is provided between the cap 9| and the uppery end of the roller support 82 to prevent the escape of the powder 63 through apertures,v not shown,- in the cap 9|.

A washer 94 is provided at the lower end of the cup-shaped member 14 in order to prevent the marble dust 63 fromescaping through the apertures 95. For the same purpose, asbestos string packing 96 is Iprovided for preventing` the escape of the marble dust 63 through the aperture 91 through which the conductor 15 extends for connection to the roller 19.

When the conductor 15 is installed in operative position, it not only tensions the coil spring 84 within the roller 19 but also it tensions the coil compression spring 99. The spring 99 is somewhat weaker than the spring 84 in order to facilitate this. When this construction is employed, it will be obvious that the spring 84 within the roller 19 provides a shock absorber action between the conductor 15 and the remaining parts of the fuse. In handling the'fuse it is likely that the roller support member 92 and parts associated therewith which are movable relative to the cupshaped retainer 14 may tend to move out of the housing 53. This movement is resisted, of course, by the conductor 15. In a low amperage fuse. the diameter of the conductor 15 is necessarily small, and, if this shock absorber action as provided by the spring 84 were not present, it is enmechanically broken during handling or installation. The spring 84 permits some relative movement of the roller support member 82 and parts attached thereto relative to the cup-shaped retainer 14, and thus eases the strain applied to the conductor 15.

The roller 19 has such a diameter and the spring 84 is arranged to revolve 'it a sufficient number of times so that the air gap which is introduced in the circuit between the ferrules 56 and 57i after the conductor 15 parts within the spacer 11 and the conductor 15 is wound upon the roller 19 is relatively great and sufdcient to prevent restriking at the voltage for which the fuse is designed to operate. The length of this air gap is relatively great as compared to the gap which would be obtained if its length were dependent entirely uponthe movementof the indicator cap 9|. It will be noted that the air gap is produced by a compact operating mechanism which is combined with an indicatorthat has a relatively short stroke. fuses of this type 4are used in cubicles and like installations wherespace is at a premium and an indicator having suilicient range of movement to provide by itself the necessary air gap would be objectionable if not entirely impracticable.

The springs 84 and 90 are so arranged and constructed that they are not. additative with respect to the application of tension to the conductor 15. Therefore, since the spring 84 is the stronger of the two springs, the tension imposed on the conductor 15 is independent of the spring 99. Therefore, the time-current characteristic This is important sinceltirely possible that the conductor 15 might be' -mdication that the fuse has operated. For this of the conductor 15, which is dependent upon the stress ,imposed on it, is not impaired by friction which may develop in the sliding indicator mechanism as would otherwise be the case if its 4time-current characteristic were dependent alone upon the force exerted by the spring 99 which moves the indicator cap 9|.

Since certain changes can be made in the foregoing construction and diderent embodiments oi the invention can be made without departing from the scope thereof, it is intended that all matter shown in the accompanying drawing and described hereinbefore shall be interpreted as illustrative and not in a limiting sense.

What is claimed as new is:

1. In a fuse device, in combination, an insulating casing, terminals at the ends of said casing, a conductor within said casing interconnecting said terminals and having one-portion that always operates first to open the circuit between said terminals on overload and another portion which operates following the operation of said one portion, a roller at one end oi said casing on which said one portion of said conductor is windable, means for moving said roller to withdraw said one portion of said conductor on operation thereof, means for rotating said roller, and indicating means held in non-indicating position by said one portion of said conductor and movable to indicating position on operation thereof.

2. In a fuse device, in combination, an insulating casing, terminals at the ends of said casing,

a conductor within said casing interconnecting ing on which said elongated portion is windable,

means for moving said roller to withdraw said elongated portion for lengthening the arc to extinguish the same, means for r'otating said roller, and indicating means heldin non-indicating posi. tion `by said elongated portion and movable to indicating position on fusion thereof.

3. In a fuse device, in combination, an insulating casing, terminals at the ends of said casing, a conductor within said Icasing interconnecting said terminals and including a fusible section, a roller within said casing over which one end of said conductor extends, means suppOIting said roller for movement longitudinally oi said casing, spring means biasing said support means and roller longitudinally of said casing and tensioning said fusible section, and additional spring means interposed between said support means and said fusible section whereby a shock absorbing action is provided therebetween.

4. In a fuse device, in combination, an insulating casing, terminals at the ends of said casing,

' a conductor within said casing interconnecting said terminals andv having one portion that always operates lrst to open the circuit between said terminals o'n overload and another portion which operates following thev operationY of said one portion, a roller at one end of said casing over which said one portion of said conductor is positioned, support means for said roller, spring means within said roller reacting between the same and said support means for biasing said roller to tension said one section, and means for moving said roller longitudinally of said casing on operation of said one portion.

5. In a fuse device, in combination, an insulating casing, terminals at the ends of said casing, a conductor within said casing interconnecting said terminals and including a fusible section, 1ndicating means movable relative to said casing from nonindicating to indicating position, spring means biasing said indicating means to indicating position, a roller carried by said indicating means over which said conductor extends, and additional spring means reacting between said roller and said indicating means, said indicating means and roller being restrained as long as said fusible section remains intact.

6. In a fuse device, an insulating casing having spaced terminals, a roller support mounted in said casing yieldingly urged outward thereof, said support being in conducting relation to one of said terminals, a roller carried by said support for movement therewith, a conductor within said casing interconnecting said terminals having at its inner portion a rst fusible section and attached to said roller for winding thereon, said conductor restraining said support against outward movement, and means for rotating said roller upon fusing of said section of said conductor.

7. In a. fuse device, an insulating casing having spaced terminals, a roller support slidably mounted in said casing yieldingly urged outward thereof and in conducting relation to one of said terminals, a roller carried by said support for movement therewith, a conductor within said casing interconnecting said terminals having at its inner portion a first fusible section and attached to said roller for winding thereon, and yielding means urging said roller in winding direction. said conductor restraining said support against outward movement and said roller against rotation.

SIGURD I. LINDELL. 

